A little stupid question.

Does range and obstruction bonus dices depends of agility modifications ?

For example, a Ghost with 3 tractor beam token, with R3 and obstruction get 2 defense dices or 0

For me, defense dices = (AGI+modifications) + Range die + obstruction die.

In the example : Defense dices = (0 (Ghost AGI) - 3 (" tractor beam token)) + 1 (R3) + 1 (obstruction) = 2

Or is it, defense dices = AGI+modifiction+range die+defense die = 0-3+1+1 = -1, so 0 defense die to roll

????

Agility and bonus dice are always calculated separately. Bonus dice are just that -- extra dice added on to whatever your agility is letting you roll. Even if your agility isn't letting you roll any dice at all.

Think of it this way: your agility is what your ship is doing to make it harder for your opponent to hit you. Range and obstacle modifications are what the environment is doing to make it harder for your opponent to hit you. And they're going to happen no matter what your ship does.

Range and obstruction bonus are NOT agility modification. The Ghost will roll 2 green dice in your example.

You're correct. Obstruction and range are added to the result of the calculation of the ship's agility, which has a minimum of 0, so a Ghost with 3 tractor tokens and both bonuses would have 2 evade dice.